Instead of using sterile water or saline, it's believed the 69-year-old woman used tap water she'd put in a filter-equipped pitcher, CBS News reported.
The amoeba got into her upper nasal cavity and then into her bloodstream, eventually reaching her brain, according to the study in the International Journal of Infectious Diseases.
This a rare case that serves as a reminder for people to follow the directions when using a Neti pot, and to use only boiled or distilled water, said Dr. Charles Cobbs, a neurosurgeon at Swedish Medical Center in Seattle who treated the woman, CBS News reported.
"She had not been boiling water, using sterile water or using sterile saline. She had been using water that had been put through a filter and maybe it had been sitting there and somehow the amoeba from somewhere else got in there. So that's what we suspect is the source of the infection," Cobbs said. "This is so rare there have only been like 200 cases ever."
Swimming in warm freshwater lakes and rivers is the most common cause of such cases, but there are rare instances where such infections occur after tap water gets into the nose, according to the U.S. Centers for Disease Control and Prevention.
This type of infection cannot occur from swallowing water, and cannot pass from person to person, CBS News reported.